Akira Yagishita

A novel analysis system of synchrotron-orbital-radiation-light induced photoemission coupled with ion scattering: SORI

Abstract We designed and constructed a novel analysis beam line connected to a 575 MeV electron synchrotron with a super-conducting magnet working at the Ritsumeikan University. It allows synchrotron-orbital-light induced photoemission and medium energy ion scattering spectroscopy under ultrahigh vacuum conditions and thus enables us to determine the electronic states and atomic configurations of surfaces and interfaces for various materials. Samples are prepared by molecular beam epitaxy and can be analyzed in situ by the above spectroscopy without exposing them to the air. The optical system consists of a cylindrical mirror for collection of the synchrotron radiation-light, a couple of plane mirrors for deflection and a varied-space plane grating as a monochromator and a toroidal mirror for focusing the monochromated light on a sample. Exchange of the varied-space plane grating monochromators of different line densities covers the photon energies from 5 up to 700 eV and the resolution ( ΔE E ) is estimated to be better than 6 × 10−4. Photoelectrons are detected with a hemispherical energy analyzer with a radius of 139.7 mm. A new toroidal electrostatic analyzer was designed and fabricated to realize a layer-by-layer analysis using medium energy ion scattering. A wide interelectrode distance of 18 mm covers a wide energy range, W( = 0.1 × E0, where E0 is the energy of ions deflected along a central curvature) at a fixed applied voltage and thus reduces the acquisition time without lowering the statistics. This paper represents the preliminary data obtained so far concerning surface hydrogen detection and surface relaxation of TiO2-terminated SrTiO3 (0 0 1).

Intense positron beam at KEK

Abstract A positron beam is a useful probe for investigating the electronic states in solids, especially concerning the surface states. The advantage of utilizing positron beams is in their simpler interactions with matter, owing to the absence of any exchange forces, in contrast to the case of low-energy electrons. However, such studies as low-energy positron diffraction, positron microscopy and positronium (Ps) spectroscopy, which require high intensity slow-positron beams, are very limited due to the poor intensity obtained from a conventional radioactive-isotope-based positron source. In conventional laboratories, the slow-positron intensity is restricted to 10 6 e + /s due to the strength of the available radioactive source. An accelerator based slow-positron source is a good candidate for increasing the slow-positron intensity. One of the results using a high intensity pulsed positron beam is presented as a study of the origins of a Ps emitted from SiO 2 . We also describe the two-dimensional angular correlation of annihilation radiation (2D-ACAR) measurement system with slow-positron beams and a positron microscope.

A compact vacuum-ultraviolet beamline for synchrotron radiation photoelectron spectroscopy combined with an ion-scattering spectrometer, SORIS.

Apparatus for high-resolution synchrotron radiation photoelectron spectroscopy combined with high-resolution medium-energy ion scattering, named SORIS, has been developed for simultaneous investigations of electronic states and atomic structures on surfaces. For this purpose, a compact vacuum-ultraviolet beamline of photon energy from 5 to 700 eV has been designed for the small storage ring Aurora installed at Ritsumeikan University. Owing to the small electron-beam size in the storage ring, an energy resolution E/dE of >5000 can be obtained.

High-resolution spherical grating monochromator for the undulator beamline (BL-16B) at the Photon Factory

The design and performance of a 24 m high-resolution spherical grating monochromator (H-SGM) for the undulator beamline (BL-16B) at the Photon Factory are described. With three interchangeable gratings of 400, 900 and 2000 lines mm(-1), the H-SGM is designed to cover the photon energy range 40-600 eV. With a resolving power of approximately 2000 in the photon energy range 40-530 eV, more than 10(11) photons s(-1) have been measured. The best resolutions obtained so far, at a substantially lower photon flux, are greater than 10 000 at 250 eV and 8000 at 400 eV